As disclosed by C. W. Tang et al in commonly assigned U.S. Pat. No. 5,550,066, the utilization of an organic material as the EL medium deposited as a single-color EL layer on a TFT array substrate has numerous advantages over liquid crystal displays (LCD) which are also commonly addressed or selectively actuated by the use of a TFT active matrix array. During the fabrication of the TFT active matrix array, Tang et al show the evolution of substantial topological surface features due to the multilayer design of the TFT array, as particularly evident in FIGS. 4, 5, 6, and 7, all of which show a TFT pixel prior to formation of an organic electroluminescent layer on an upper surface thereof. A single-color EL organic layer 82 is shown in FIGS. 3, 8, and 9 of the above U.S. Pat. No. 5,550,066 as extending with uniform thickness along the entire surface of TFT pixel, as a layer conforming to the topological features of the pixel. Conventional vacuum evaporation was employed as the physical vapor deposition method in forming the EL organic layer. This single-color EL layer did not have to be patterned because the layer only emits light in that region of the pixel where the layer is in electrical contact with both a transparent (ITO) anode bottom electrode and a top electrode 84. Thus, the lateral position of the ITO transparent anode bottom electrode 72 within the pixel provides effectively a self-patterning feature for this single-color (monochrome) device. Each pixel has raised surface portions and a recessed surface portion which also reveals the transparent anode bottom electrode. In a two-dimensional array of such pixels, the deposition of a single-color forming conformal EL layer over the entire surface area of each of the pixels, is advantageous from the viewpoint of simplicity of manufacturing, since such a single-color forming EL layer does not have to be patterned.
For full-color displays, however, it is necessary to provide a suitable method of patterning each pixel of an EL display into three color subpixels capable of generating red, green, or blue light. The present invention provides such methods of patterning, taking advantage of the TFTs topological surface features to form a full-color organic EL display.